1. Field of the Invention
The present invention relates to a process of chemically separating uranium isotopes. More particularly, the invention relates to a process of separating or concentrating uranium-235 from a solution containing uranium-238 and uranium-235 which comprises passing a solution of a reducing agent through an anion exchange material retaining uranium in the form of uranium (VI) complex anions. The solution of the reducing agent elutes the uranium ions and at the same time reduces the uranium (VI) complex anions to uranium (IV) complex ions.
2. Description of the Prior Art
Various attempts have hitherto been made for chemically separating uranium isotopes but it has been believed to be impossible to separate or concentrate uranium isotopes on an industrial scale or manner by utilizing ion exchange materials even though many ion-exchange separation processes for uranium isotopes have been reported. For example, Shimokawa et al. U.S. Pat. No. 3,511,620 discloses a process in which a solution of U(VI) ions enriched with .sup.235 U is obtained by eluting the U(IV) ions absorbed on a cation exchange resin with a solution of a salt of Fe (III). However, in such a process as mentioned above, .sup.235 U is only obtained as a solution of U(VI) ions by a single stage oxidation reaction, the multiplied concentration effects for .sup.235 U are not obtained, and hence a high degree of enrichment of .sup.235 U can not be obtained.
In Japanese Patent Application Laid Open No. 12700/72, a process for concentrating .sup.235 U is disclosed. The process comprises passing a solution of U(IV) ions through a cation exchange resin in equilibrium with a reducing agent to convert a part of the ion exchange resin to the U(IV) form and passing further a solution of an oxidizing agent through the cation exchange resin to move the uranium ions through the cation exchange resin as U(VI) ions, whereby the U(VI) ions are converted to U(IV) ions again by the action of the reducing agent of the cation exchange resin and adsorbed as the U(IV) ions on the cation exchange resin in a form of an adsorbed band or region, and then .sup.235 U is enriched in the U(IV) ion band near the boundary between the U(IV) ion band and the reducing agent or the oxidizing agent.